Windley U.S. Pat. No. 3,971,202 describes the cobulking of electrically conductive sheath-core filaments such as are disclosed in Hull, U.S. Pat. No. 3,803,453, with nonconductive filaments to form a composite yarn. The conductive filaments are melt-spun at a rate of about 890 yards per minute, ypm, (meters per minute, mpm) and then drawn at least about 2.0.times. on a draw twister, to increase tenacity. The strength is needed for subsequent processing, e.g., in the hot cobulking jet with the nonconductive fibers. The separately drawn conductive and nonconductive filaments are then combined on a roll in a hot chest where they are annealed to reduce shrinkage and then the combined yarns are cobulked.
Unfortunately, conductive filament breaks occur frequently at or about the location where the filaments are combined. Further, cross-overs of the conductive filaments between ends of nonconductive filaments on the roll take place thereby reducing the proportion of first quality product that is obtained. The solution to these problems has been a desirable objective.